Printing apparatus blanket and method of making same



Dec. 5, 1933. l.. SMITH ET A1. 1,938,301

PRINTING APPARATUS BLANKET AND METHOD OF MAKING' SAME Filed March 20, 1951 NIA A A A ,IWA A A A n 7/////////////////////////////////////////////////////////// VAVA AVA M7 V VAWxVA A ////////////////////////////////////////////ff////f/f/M/4 v vvvvvvn Patented Dec. 5, 1933v PRINTING APPARATUS BLANKET AND METHOD OF MAKING SALIE Louis Smith, Lombard, Ill., and Fred Vogel, Grand Haven, Mich.; said Vogel assigner to said Smith Application March zo, 1931.' serial No. 5214.212

s claims. (c1. 154-545) This invention relates to improvements in blankets adapted for application to offset` and printing cylinders, newspaper, fiat-bed, offset and proving presses; and to the method of preparing blankets embodying the invention.

Blankets of the character referred to are well adapted for use on proof and transfer cylinders of various types of machines for making printing plates, including offset printing plates and litho- 1o graph printing plates, one example of such machines being described in United States Letters Patent No. 1,584,483 of May 11, 1926.

The main object of the present invention is to produce a blanket, the outer surface of which is u relatively hard but flexible, and non-penetrable by any cleansing materials which are used in printing and offset printing, and non-penetrable by oils, moisture or ink. Another object is to produce a blanket, the base of which is sufficient p ly firm in texture to prevent spreading and o stretching but resilient enough to give the deairedY cushion effect behind the outer or contact surface.

A blanket constructed in accordance with our 35 invention may be cleansed by merely wiping it with a moist cloth and since the ink does not penetrate the specially prepared outer coating, the blankets may be used repeatedly.

' The composition of the base of the blanket beneath the outer coatings is such that when the outer surface is subjected to pressure, in normal use, the blanket will not stretch or spread unduly, but will function as a cushion behind the outer surface whereby the latter presents a smooth face and makes uniform and perfect impressions on the printing element.

Another feature of the invention is the method of applying various coatings to the base of the blanket whereby the surface coatings are rendered 40 flexible and the blanket, as a whole, may be applied to a cylinder without stretching or becoming wrinkled.

By employing the blanket of our invention for making zinc printing plates, one negative printing object may be multiplied to several positives on one cylinder. When such cylinder has been positioned and locked to another cylinder, and the objects transferred, the second cylinder will constitute a negative, and from said negative, the

objects may be transferred to a zinchprinting plate positive, for offset printing. Ink'will not adhere to our improved blanket when multiplying one impression to several on the blanket surface. Further objects and advantages will appear from the following specification: f

Fig. 1 of the accompanying drawing shows a fragmentary cross sectional view of a blanket embodying our invention.

Fig. 2 of the drawing shows a fragmentary cross sectional View of a blanket embodying a modification of the invention.

As a base material for the blanket, shown in Fig. l, we preferably employ three to five plys of ne or coarse fabric depending on the caliper blanket desired, with thin layers of rubber between the fabric pieces, the alternate layers being firmly cemented and pressed together to form a base which is flexible and resilient but rm enough to resist stretching and spreading.

The upper surface of this fabric and rubber base may consist of either a layer of the rubber or of the fabric which compose the base. If the upper surface consists of fabric we prefer to fill the pores of the fabric with dope before applying the moisture, oil and ink proof top surface. The dope coating preferably consists of three coats, the first being a 10 ounce gun cotton and castor oil and rape seed oil solution and the second and third coats being 8 ounce solutions. By this we mean that the proportion of gun cotton to the solvent is 10 ounces of gun cotton to one gallon of the,solvent for the first coat, and 8 ounces of gun cotton to one gallon of the solvent for the second and third coats. The coats are preferably driedV at room temperature for a pe- 85 y riod of four to five hours each. After the dope coatings have been applied to the blanket base it is rolled between pressure rolls to insure a smooth nish and uniform thickness of the blanket.

, Above the dope coatings we preferablyapply three or four coatings of varnish to which pigment may be added. The varnish may be flow or spray coatings, applied with a brush or spray, but we prefer to apply the varnish coats as well as the dope coats by means of 'revolving rollers, 95 partially immersed in the material to be applied, and located in juxtaposition to the surface o1'- the blanket to be coated. The blanket to be coated, of any desired length, is preferably arranged inthe form of a loop over spaced apart rotating conveyor rolls which cause the blanket to travel in the manner of an endless belt. Thus parts of the blanket are alternately traveling in a horizontal plane and over an arcuate surface. The roller for applying the coatings is preferably located opposite one of the conveyor rolls so that the several coatings are applied to the base while it is resting on thecurved surface of one of the conveyor rolls. These rolls shall have the same circumference as the rolls. used in making the fabric and rubber base, so that curved supporting surfaces of substantial dimensions will be presented for the blanket to rest upon while the coatings are being applied.

The three or four varnish coats which are thus applied to the dopecovered surface of the base are preferably dried at 150 F. with about eighteen hours between coats, but the temperature and drying time may be varied.

'The blanket just described, which consists of the fabric and rubber base with dope coatings intermediate said base and outer varnish .coatings, presents a flexible but hard surface, nonpenetrable by oil, ink or moisture, and is particularly suitable for newspaper work.

Referring now to Fig. 2, a slightly softer outer nish, very desirable for offset plate making machines and offset proving press work, may be produced by using the following mentioned materials, the method of application being the same as that heretofore described:

Three to ve plys of fabric with layers of rubber between them and a layer of rubber on the upper surface of the fabric are pressed and cemented together into a flexible but firm base. On

top of the outer rubber coating we prefer to apply three black varnish coats. These coats are made of ordinary varnish and coach black. The coach black lls the pores of the rubber without deleteriously affecting the rubber. After each of these varnish and coach black coats have dried, preferably at 150 F., we apply two coats of varnish to which pigment may be added if desired.

The coach black and varnish coats herein mentioned, located just above the top rubber layer of the base, may be prepared by boiling sixtyfive gallons of linseed oil to approximately 575 F. to the consistency of heavy paint oil, mixing twenty pounds of lamp black with twenty gallons of naphtha, and adding Same to the sixty-ve gallons of linseed oil at the reducing point of 300 F. Four pounds and one ounce of burnt umber may be added to the mixture as a drier, preferably added when the oil reaches 250 F., and is boiled with the oil.

The two varnish coats applied above the coach black and varnish coats are m de of fifty gallons of linseed oil boiled at 550-57 F. until it draws fine hair strings when tested. When the oil reaches 250 F. ten pounds of japanner's brown are added and boiled with the oil. When the oil reaches the reducing point of 300 F., fifty gallons of naphtha are added. Any desired pigment ground in linseed oil may be added to the varnish coatings.

The coarseness of the fabric used in the base, and the relative thicknesses of rubber layers and fabric, may be varied, depending on the kind of fabric and the requirements of the work. Coarse fabric is less likely to stretch than is fine fabric and is particularly desirable for newspaper Work. However, if the fabric of the base is too coarse the inequalities of the bottom surface of the blanket will be transmitted through the blanket to the work and this is to be avoided. The total thickness of the 'finished blanket for offset presses is preferably ,0065 to .0067 and for newspaper work the thickness may vary from .0065 to .0117 inches.

We claim:

l. A blanket for printing apparatus comprising a base consisting of alternate layers of fabric and rubber cemented and pressed together, the upper surface of said base consisting of a fabric layer, n. dope coating applied to the upper fabrf; Sheet,

said dope coating consisting of a plurality of coats of a gun cotton, castor oil andrape seed oil solution, and a plurality of coatings of varnish on top of the dope coating.

2. A blanket for printing apparatus comprising a base consisting of alternate layers of fabric and rubber cemented and pressed together, the

upper surface of said base consisting of a fabric layer, a dope coating applied to the upper fabric sheet, said dope coating consisting of three coats of a gun cotton, castor oil and rape seed oil solution, and three coatings of varnish on top of the dope coating.

3. A blanket for printing apparatus comprising a base consisting of a plurality of alternate layers of fabric and rubber, cemented and pressed together, the upper surfaceof said basefconsisting of a rubber layer, a plurality of coats, each consisting of varnish and coach black, applied to the upper rubber layer, and a plurality of varnish coats applied to the upper coach black and varnish coat.

4. A blanket for printing apparatus comprising a base consisting of a plurality of alternate layers of fabric and rubber, cemented and pressed together, the upper surface of said base consisting of a rubber layer, three coats, each consisting of varnish and coach black, applied to the upper rubber layer, and two varnish coats applied to the upper coach black and varnish coat.

5. A blanket for printing apparatus comprising a base consisting of a plurality of alternate layers of fabric and rubber, cemented together, the upper surface of said base consisting of a rubber layer, a plurality of coats, each consisting of a mixture of linseed oil, lamp black and naphtha, applied to the upper rubber layer, and two varnish coats' consisting of linseed oil, japanners brown and naphtha applied to the upper of said rst mentioned coats.

6. The method of making blankets for printing apparatus which consists in preparing a base by cementing and pressing together alternate layers of fabric and` rubber sheets, with a fabric sheet forming the top surface of the base, applying a plurality of dope coatings consisting of a gun cotton, castor oil and rape seed oil solution, each of said coatings being dried at' room temperature for a period of four to iive hours, rolling the dope coated base between pressure rolls, then applying a plurality of varnish coatings to the dope coated base.

7. The method of making blankets for printing apparatus which consists in preparing a base by cementing and pressing together alternate layers of fabric and rubber sheets, with a fabric sheet forming the top surface of the base, applying a plurality of dope coatings consisting of a gun cotton, castor oil and rape seed oil solution, each of said coatings being dried at room temperature for a period of four to ve hours, rolling the dope coated base between pressure rolls, then applying a plurality of varnish coatings yto the dope coated base, said varnish coats being dried at about 150 F. and applied at approximately eighteen hour intervals.

8. The method of making blankets for printing apparatus which consists in cementing and pressing together alternate layers of fabric and rubber to form a base, a rubber layer constituting-the top surface of the base, applying to the rubber surface a plurality of blackfvarnish coats consisting of linseed oil, lamp black,- and naphtha, each of said coats being dried at approximately surface a plurality of black varnish coats consisting of linseed oil, lamp black, burnt umher, and naphtha, each of said coats being dried at approximately 150 F., and then applying a. plurality of varnish coats above said black varnish coats.

LOUIS SMITH. FRED VOGEL. 

